I think many puranas describe how a Sanyasi should be. Part 4 Chapter 2 (Pg 1680) of Shiva Purana describes in three chapters. Dspace is dead now and try to see Kalasamhitha Section chapter 3 of Shiva Purana from Indian Scriptures.
– The Destroyer♦Mar 28 '16 at 7:50

3 Answers
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Vishnu Purana, Book 3, Chapter 9 describes about the four orders of life: Brahmacharya, Grihastha, Vanaprastha and Sanyasa. In Vanaprastha, one prepare himself for Sanyasa, so I am mentioning all the properties of these two Ashramas.

Description of Vanaprastha Ashrama

When the householder, after performing the acts incumbent on his condition, arrives at the decline of life, let him consign his wife to the care of his sons, and go himself to the forests. Let him there subsist upon leaves, roots, and fruit; and suffer his hair and beard to grow, and braid the former upon his brows; and sleep upon the ground: his dress must be made of skin or of Káśa or Kuśa grasses; and he must bathe thrice a day; and he must offer oblations to the gods and to fire, and treat all that come to him with hospitality: he must beg alms, and present food to all creatures: he must anoint himself with such unguents as the woods afford; and in his devotional exercises he must be endurant of heat and cold. The sage who diligently follows these rules, and leads the life of the hermit (or Vánaprastha), consumes, like fire, all imperfections, and conquers for himself the mansions of eternity.

Description of Sanyasa Ashrama

Let the unimpassioned man, relinquishing all affection for wife, children, and possessions, enter the fourth order. Let him forego the three objects of human existence (pleasure, wealth, and virtue), whether secular or religious, and, indifferent to friends, be the friend of all living beings. Let him, occupied with devotion, abstain from wrong, in act, word, or thought, to all creatures, human or brute; and equally avoid attachment to any. Let him reside but for one night in a village, and not more than five nights at a time in a city; and let him so abide, that good-will, and not animosity, may be engendered. Let him, for the support of existence, apply for alms at the houses of the three first castes, at the time when the fires have been extinguished, and people have eaten. Let the wandering mendicant call nothing his own, and suppress desire, anger, covetousness, pride, and folly. The sage who gives no cause for alarm to living beings need never apprehend any danger from them. Having deposited the sacrificial fire in his own person, the Brahman feeds the vital flame, with the butter that is collected as alms, through the altar of his mouth; and by means of his spiritual fire he proceeds to his own proper abode. But the twice-born man, who seeks for liberation, and is pure of heart, and whose mind is perfected by self-investigation, secures the sphere of Brahmá, which is tranquil, and is as a bright flame that emits not smoke.

SB 7.13.2 — A person in the renounced order of life may try to avoid even a dress to cover himself. If he wears anything at all, it should be only a loincloth, and when there is no necessity, a sannyāsī should not even accept a daṇḍa. A sannyāsī should avoid carrying anything but a daṇḍa and kamaṇḍalu.

SB 7.13.3 — The sannyāsī, completely satisfied in the self, should live on alms begged from door to door. Not being dependent on any person or any place, he should always be a friendly well-wisher to all living beings and be a peaceful, unalloyed devotee of Nārāyaṇa. In this way he should move from one place to another.

SB 7.13.4 — The sannyāsī should always try to see the Supreme pervading everything and see everything, including this universe, resting on the Supreme.

SB 7.13.5 — During unconsciousness and consciousness, and between the two, he should try to understand the self and be fully situated in the self. In this way, he should realize that the conditional and liberated stages of life are only illusory and not actually factual. With such a higher understanding, he should see only the Absolute Truth pervading everything.

SB 7.13.6 — Since the material body is sure to be vanquished and the duration of one’s life is not fixed, neither death nor life is to be praised. Rather, one should observe the eternal time factor, in which the living entity manifests himself and disappears.

SB 7.13.7 — Literature that is a useless waste of time — in other words, literature without spiritual benefit — should be rejected. One should not become a professional teacher as a means of earning one’s livelihood, nor should one indulge in arguments and counterarguments. Nor should one take shelter of any cause or faction.

SB 7.13.8 — A sannyāsī must not present allurements of material benefits to gather many disciples, nor should he unnecessarily read many books or give discourses as a means of livelihood. He must never attempt to increase material opulences unnecessarily.

SB 7.13.9 — A peaceful, equipoised person who is factually advanced in spiritual consciousness does not need to accept the symbols of a sannyāsī, such as the tridaṇḍa and kamaṇḍalu. According to necessity, he may sometimes accept those symbols and sometimes reject them.

SB 7.13.10 — Although a saintly person may not expose himself to the vision of human society, by his behavior his purpose is disclosed. To human society he should present himself like a restless child, and although he is the greatest thoughtful orator, he should present himself like a dumb man.

Physical activities of mere "procedures" cannot define the true form of SannyAsa. If it were true then won't it become the guaranteed way to achieve the ultimate bliss?
To answer your Q, I don't know which scriptures have the basis for this. This is a partial answer :-)

Why SannyAsa?

The closest English is Retirement. A wise analytic (SAmkhya) doesn't opt for SannyAsa just because of tiredness, laziness or fear of failure. But he/she is convinced that whatever "I do" is just an interaction of Prakruti's 3 modes; in reality "I don't do anything at all":

Why should one worry about worldly matters, when those are not in control anyway! How much ever one pushes to a building, it won't move a bit; then why to push?

Akarma based SannyAsa

If Karma is renounced then automatically its reward is also renounced. This is a very strong argument for everyone to renounce their Karmas or going on the path of Akarma, the conventional form of SannyAsa.
Below are the challenges faced:

Practicality: It's simply impossible to have a body in Prakruti's 3 modes & refraining from doing any Karma, i.e. complete Akarma is impossible. To sustain a body, one needs to breath, eat, walk, sleep, & perform daily activities. Even just imagining "I don't do Karma" is also a Karma. Hence the SannyAsa based on complete Akarma has to be rephrased as, "mostly generating Akarmas"; in other words "avoiding as many Karmas as possible".

BG 3.4, 3.5, 3.6 — By not starting Karma, '[the state of] not doing Karma' is Not achieved by Purusha(consciousness); and (by) Retirement(complete Akarma based SannyAsa) really doesn't result in way to SamAdhi(Moksha).
— Anyone for a moment doesn't sustain by generating only Akarma; All have to do Karma under control of [3] modes born out of Prakruti.
— By controlling sense from (doing) Karma, whose mind (still) dwells for senses, such foolish self (mUdhAtma) is called to be under MithyAchAra (worthless efforts)

If one's mind is already retired from sense gratification, then the purpose of SannyAsa is fulfilled. So called "procedures" are irrelevant after that. Usually under influence of Tamas, some believe that the physical "procedures" are necessity. It can be termed as Vikarma.

Akarma Sanga (Attaching with 'not doing something'): Akarma Sangahappens due to conscious concern towards Akarma. It's a failure in developing "indifference" towards certain matters.
e.g. a point listed is "Strictly observe celibacy". Celibacy has to be neither "strict" nor be "explicitly observable". Both of these might attach one towards "not having sex", which is as wrong as attaching to "having sex"! One is too much concerned towards "not doing 'it', not doing 'it', ...".
This is Akarma Sanga, where a person's focus is deviated from supreme One to "not doing 'it'".

BG 2.47 — You have only power to (do) Karma, not anytime into reward; Let not Karma happen for reward purpose; Let not be attached to Akarma.

Rather celibacy should be a byproduct of one's lifestyle. e.g. A married soldier while on war, naturally doesn't get involved in masturbation or sexual activity. When he is with his wife, he naturally gets involved in such pleasures. In fact, "Sexual pleasure" is never his concern; he is indifferent to sex. That is plain Akarma, & no Sanga. "Sex" is a physical process, let's not associate it with "Celibacy", which is a state of mind.

Karma Yoga based SannyAsa

Akarma based SannyAsa was prevalent during ancient times as well. But practically everyone has to do certain Karmas to sustain self, be it too less. How much less is subjective & personal. Hence, Krishna redefined it as Karma yoga only!

SannyAsa = [Renouncing reward of Karma] or [Karma Yoga]

In Gita, Karma Yoga is also simply called Yoga at many places, because everyone has to do Karma anyways; so prefixing "Karma" is redundant.
Below are few definitions of SannyAsi:

BG 5.3 — O mighty armed, Know him(her) to be always SannyAsiwho neither has disliking nor desires; free from dilemma, is certainly liberated from bondage happily.BG 6.2 — O PAndava, what is said as "SannyAsa", know it to be (Karma) Yoga; Anyone without retiring from vows doesn't become Yogi.BG 6.4 — Only when engaged neither for senses nor in Karma of all vows, a SannyAsi is said to be elevated in Yoga.BG 18.2 — Resigning from desire-ful Karma is known as SannyAsa among wises; Renouncing the reward of Karma is called "renunciation" by clever.

As you may see that, true SannyAsa is about being "disengaged from vows" (if any); and not otherwise.

Choice

If both are correct, then which SannyAsa should be chosen: Akarma based or NishkAma Karma based?

From this answer: 'Married or unmarried, a man can realise the Self'
– sv.Mar 28 '16 at 15:40

I think how a Sanyasi should be is specifically mentioned in precise and simple terms in scriptures.Also,the person who compiled the infos in that blog is as per me a knowledgble Brahmin wjo knows very well what he is talking about.i guess he compiled informations from more than one Puranas and other Dharma sastras in one post.So unless one is very well versed in sastras one can't possibly correctly answer my question."Physical activities of mere "procedures" cannot define the true SannyAsa"-This seems to be a personal opinion which denies scriptures.Btw nice attempt :)
– RickrossMar 29 '16 at 6:07

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@sv., yes it's true. Thanks, I have covered that point into my answer with bit more detail. People usually think like this: "Marriage" ==> "Sex" ==> "No celebacy" ==> "No realization". It's naive to associate "physical process" ("sex") with "mental state" ("celibacy"). We often see that among 2 students, 1 read for an hour and other reads for 8 hours, still the 1 hour kid understands better. "Reading" is physical process and "Understanding" is mental state. People relate them blindly and hence such crooked system is created.
– iammilindMar 29 '16 at 7:23

There are a few Upanishads that describe what sannyas is and what the actions are to be followed. Those Upanishads are: Bhiksuka Upanishad of Sukla Yajurveda, the Naradaparivrajaka Upanishad of Atharvanaveda, and the Aruneyi Upanishad of the Atharva-veda. The first is very short, essentially one verse, the last only 5 verses.

What the 'duties' (and I use the word loosely since a sannyasin has no duties) are depends upon what kind of sannyas a person is. The Bhiksuka Upanishad starts with (Thirty Minor Upanishads, K Narayanasvami Aiyar translator):

Among religious medicants (bhiksus) who long for salvation (moksa), there are four kinds, viz., kuticaka, bahudaka, hamsa and paramahamsa.

The 'rules' vary between the different types of sannyas mentioned above, but don't map for the most part to the link you provided. For instance, the same Upanishad says:

Then the hamsas should live not more than a night in a village, five nights in a town and seven nights in a sacred place,...

To answer or refute each point in the link provided would be too lengthy an answer.

I think its wise to take a look at what the Puranas are saying on this.They must be more clear and precise on topics such as this.Elaboration and elucidation of the most terse esoteric & sophisticated knowledge found in the Vedas in simpler terms was needed.And that's precisely why God spoke out the Puranas and Vyasa compiled them.If Vedas were sufficient then Puranas won't have existed.I think more precise definitions of the duties and traits of a perfect Sanyasi is laid down in the Puranas.
– RickrossMar 30 '16 at 17:53

*I would have loved an answer based on that.Anyways the comments under the question are helpful and so is ur answer .Upvoted.
– RickrossMar 30 '16 at 17:53